Drive systems of the type in which a driven belt engages a movable rack are described, for example, in German Pat. No. 29 10 373. The arrangement permits highly precise controlled positioning of the movable element by providing for conversion of rotary movement, for example of an electric motor to which a drive gear or similar element is coupled, into linear movement of the slider or carriage, or other element to be positioned. The arrangement is capable of positioning the movable element over long distances without play or slippage, thus providing for high positioning accuracy over long paths. The rack, in such arrangements, usually was made as one or more steel rail; if a plurality of rails are used, they can be assembled, linearly, to extend the length of the positioning path. The rack itself is made by milling the rack teeth into the steel rail. The rack may, however, also be made of the same material as the gear or tooth belt, and bonded to a carrier rails, for example by adhesives.
Long racks, for example made by milling of a steel rail, are expensive; as the length of the racks increases, the cost of making accurately formed racks increases rapidly. Additionally, the racks require complex and expensive support constructions so that the rack and guide rods or the like to define the guide path, are in predetermined alignment or position with respect to each other. This is particularly so if the loads to be carried by the movable element are large. The movable element, typically, can be used to carry automatic machine tools, robots, or other handling apparatus. All those are heavy. The arrangement of a belt engaging a rack, however, is particularly suitable for such drives because the position of the movable element with respect to the base element or base or frame of the entire system can be accurately controlled.